1. Technical Field
The present invention relates to a digital broadcast receiving system for receiving an MPEG (Moving Picture Experts Group) 2 format broadcast transport stream of video data and audio data and transmitting the received stream to a digital signal processing device through an IEEE (Institute of Electrical Electronic Engineers) 1394 interface. The present invention also relates to a receiving device using such a system.
2. Related Art
In recent years, the IEEE 1394 interface that allows video data and audio data to be transferred between digital video devices and digital audio devices at high speed are becoming common. The IEEE 1394 interface supports both the isochronous transfer mode and the asynchronous transfer mode. The isochronous transfer mode is suitable for transferring a chronologically successive data stream of video data and audio data at high speed. On the other hand, the asynchronous transfer mode is suitable for transferring various commands.
Recently, digital broadcasts are becoming common. In a digital broadcast, a digital video signal and an audio signal are compressed corresponding to the MPEG2 format. In addition, a plurality of programs are multiplexed and transmitted. When a digital broadcast is received, an-IRD (Integrated Receiver Decoder) is connected to a television receiver. The IRD selects a signal of a program that the user desires and decodes the selected signal into a video signal and an audio signal. An output signal of the IRD is supplied to the television receiver.
A structure of which the IEEE 1394 interface is connected to the IRD that receives a digital broadcast has been proposed. When the IRD has the IEEE 1394 interface, the IRD is connected to a digital video recording/reproducing device through the IEEE 1394 interface. Thus, a digital broadcast receiving system can be structured.
As was described above, when the system of which the IRD is connected to the digital video recording/reproducing device through the IEEE 1394 interface is used, data can be easily transferred from the IRD to the digital video recording/reproducing device and recorded thereto.
In addition, the IEEE 1394 interface allows command to be transferred in addition to digital video data and digital audio data. Thus, a timer record operation can be easily performed. For example, when a program record start time is set up on the IRD side, at the program record start time, the IRD transfers a record start command to the digital video recording/reproducing device. Thus, the digital video recording/reproducing device enters the record mode and records data received from the IRD.
A program transmitted by a digital broadcast contains copyright information for protecting the copyright thereof. The copyright information is contained as two descriptors (DM_copy_control_descriptor) and (digital_copy_control_descriptor) in a PMT (Program Map Table) of a transport stream in such a manner that the copyright information of the service (program) is associated with the contents data.
The script (DM_copy_control_descriptor) contains information of an analog video output. On the other hand, the script (digital_copy_control_descriptor) contains information of CGMS (Copy Generation Management System) or M-CGMS( ) that is information of a digital video output.
Thus, in the digital broadcast receiving system of which the IRD is connected to the digital video recording/reproducing device through the IEEE 1394 interface, when a timer record operation is performed, it is necessary to notify the user whether or not a program that will be recorded with the timer record operation is copy-prohibited. In addition, in a digital broadcast, there are two prohibition modes that are a digital record prohibition mode and an analog record prohibition mode. Thus, it is necessary to notify the user whether or not a program is prohibited in the analog record prohibition mode or the digital record prohibition mode.
In addition, there are many adverse cases that when the timer record operation is performed, output data of the IRD is being recorded by another device; the digital video recording/reproducing device is operating; a tape or a disc is not loaded to the device or in record protect state. When the timer record operation is executed in such cases, data recorded on a tape may be destroyed. Alternatively, the device may malfunction. Thus, in such cases, it is desired to cancel the timer record operation and to notify the user of a cause of the cancellation of the timer record operation.
Therefore, an object of the present invention is to provide a digital broadcast receiving system and a receiving device that allow the timer record operation for a program to be prohibited so as to protect the copyright thereof.
Another object of the present invention is to provide a digital broadcast receiving system and a receiving device that cause the timer record operation to be canceled in the case that the timer record operation cannot be executed and allow the user to be notified of a cause of the cancellation of the timer record operation.